Heart failure is a condition effecting millions of people worldwide. Heart failure includes failure of either the left side of the heart, the right side of the heart, or both. Left heart failure can lead to elevated pulmonary venous pressure, which may cause respiratory problems, including shortness of breath and exercise intolerance. Left heart failure may be ascribed to a number of causes, including valve disease, systolic failure of the left ventricle, and diastolic failure of the left ventricle. The adverse clinical result of each of these conditions is similar; the heart failure leads to elevated pressure in the left atrium and elevated pressure in the pulmonary veins, impeding proper flow of oxygenated blood through the blood supply. Therefore, there exists a need to treat the symptoms of left heart failure on the body.
Heart failure has been further classified as either systolic heart failure or diastolic heart failure. Diastolic heart failure refers to heart failure that is present without the presence of major valve disease even while the systolic function of the left ventricle is preserved. More generally, diastolic heart failure is failure of the ventricle to adequately relax and expand in order to fill with blood, causing a decrease in the stroke volume of the heart. Presently, there exist very few treatment options for patients suffering from diastolic heart failure. Therefore there exists a need for methods and devices for treating symptoms of diastolic heart failure.
Some types of pressure relief shunts have been used to treat the symptoms of diastolic heart failure. Examples of such types are disclosed in U.S. Pat. No. 8,043,360 and U.S. Published Patent Application No. 2011/0295366 A1. The long term effects of the creation of a pressure relief shunt can vary greatly depending on the amount of blood flow through the shunt. These effects can include the gradual development of hypertrophic pulmonary arteries for cases with significant left to right shunting. The hypertrophy of the pulmonary arteries in turn leads to worsening symptoms of heart failure. At the other end of the spectrum, the long term effect of the creation of a pressure relief shunt may include a gradual decrease in the amount of blood passing through the shunt such that the benefit of the procedure may be reduced or eliminated.
The hemodynamic conditions associated with diastolic heart failure are not static, and attempting to treat the disease with a static pressure relief shunt represents a deficiency in the prior art. For example, if a shunt is sized too large the short term effect of the creation of a pressure relief shunt may include a sudden worsening of heart failure. This phenomenon has been reported in similar procedures for heart failure patients and may be considered a type of rebound stress. Furthermore, if the pressure relief shunt is sized too small the patient may not experience any clinical improvement from the procedure. The size of the pressure relief shunt required for efficacious treatment of diastolic heart failure may be difficult to predetermine, and varies with the condition of the patient and with the state of the underlying disease. With these deficiencies in mind, there still exists a need, among other needs, for an adaptive means of treating diastolic heart failure by creating a clinically effective and safe pressure relief shunt.
Along those lines, deployment techniques exist for creating a pressure relief shunt in the atrial septum and then gradually allowing the shunt to open by slowly deflating a balloon which initially occludes the shunt. For example, the balloon may be gradually deflated over a period of hours our days. This treatment method and apparatus suffers from deficiencies. For example, the requirement to leave a balloon in place in order to gradually open the pressure relief shunt can create significant problems such as the problem of keeping the balloon in place despite the significant pressure differential across the shunt. Furthermore, the requirement to leave a catheter dwelling within the circulation carries significant potential risks, including increased risk of pulmonary embolism, sepsis, sensitization or allergic reaction, and other potentially adverse clinical reactions.
The constantly evolving nature of heart failure represents a significant challenge for the treatment methods currently disclosed in the prior art. Therefore, there is still a need for novel and adaptable methods and devices for treating diastolic heart failure by creating a pressure relief shunt which can be retrieved, repositioned, adjusted, expanded, contracted, occluded, sealed or otherwise altered as required to treat the patient. Furthermore, there exists a need for devices and methods for treating diastolic heart failure which can automatically self-adjust over time either in accordance with the gradual hemodynamic changes associated with heart failure or in anticipation of these changes.